Computing systems may maintain user identifiers (IDs) that provide for authentication and authorization of users with such systems. Collectively, a set of user identifiers may constitute a user ID space. Two entities with separate computing systems may wish to collaborate and communicate about the individual people that maintain user accounts in each of their respective user ID spaces. For example, two merchant partners may maintain separate computing systems with distinct user ID spaces, and may want to identify areas of overlap between their respective merchant loyalty programs for offering services and/or benefits to the people that are members of both loyalty programs.
Unfortunately, the user ID space of each entity may be very large and the respective computing systems may each use a different user ID to reference the same individual person. In addition, the technical capabilities and resources of one or more of the entities may be limited and reconciling user ID spaces may be challenging. Accordingly, without sharing sensitive personal identifiable information (e.g., name, telephone number, address, and the like) about their respective users, reconciling two or more unique user ID spaces between multiple computing systems may be a difficult if not at least complex and time consuming task.